Professor Gely, from the Labor Prof Blog, has a link to an abstract of a recent study surveying more than 50,000 Californians who self-identified based on their sexual orientation and how that affected their earnings. Although I haven't read the article itself, the abstract seems to have some contradictory statements. This statement:

Apart from the well-documented marriage premium, the author finds no statistically or economically significant independent effect of a gay or lesbian sexual orientation on earnings.

Does not seem to square with this one:

Researchers using the 1988-96 General Social Survey (GSS) have found that behaviorally gay/bisexual men earn 15-30% less, and behaviorally lesbian/ bisexual women earn 20-30% more, than similar heterosexuals.

If the latter is true, in addition to seeming to disprove the first statement, it would be interesting to know why.